Early diagnosis and monitoring of the progression and regression of atherosclerosis have a crucial importance in the fight against the world's number one fatal heart disease. Magnetic resonance imaging and spectroscopy methods provide valuable information about the morphology and chemical composition of atherosclerotic plaques but suffer from low signal-to-noise ratio and low image resolution. We propose to develop a new intravascular magnetic resonance imaging method that will involve using an MR probe on the tip of a catheter. This will allow more complete characterization of atherosclerotic plaques as well as providing a novel method of monitoring interventional therapy that is not currently possible. The specific aims of this project include the development of a novel real-time MR fluoroscopy technique (5 frames/sec) for 3-D visualization of a catheter probe, and the development of novel encoding techniques to achieve near-microscopic resolution imaging (100 microns) and highly localized spectroscopy. The applicants proposed to validate these techniques on phantoms, dogs and on a high cholesterol-fed atherosclerotic rabbit model. The development of intravascular magnetic resonance techniques will lead to an innovative, practical system that will be used routinely for the diagnosis of atherosclerosis as well as for monitoring various interventional techniques such as laser therapy.